My sister was doing homework when I got back home yesterday.
I was cooking while talking on the phone.
There is nothing wrong as you can see.
Hand the homework as soon as you finished.
He won't be here until 7:00 pm.
I got back home after 10:00 pm last night.
He always gets up before 8 in the morning.
PS:when,while这些从句,一般都是放在句子后面的.